<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>添加新属性</title>
</head>
<body>
<p id="demo"></p>
<script>
  var person = {
    firstname:"Bill",
    lastname:"Gates",
    age:62,
    eyecolor:"blue"
  };
  person.nationality = "English";

</script>
</body>
</html>